Download Function - MrsHBraaten

Cell Structure and Organelles
Protoplasm is all material in a cell,
nucleus and cytoplasm
Background information on cell
structure
• Cells differ greatly in size - from a pneumonia
bacterium (0.0001 mm in diameter), to a
human egg cell (0.2 mm in diameter) to a
human nerve cell (which can reach 1 m in
length) to an ostrich egg (75 mm in diameter).
Because cells have many different functions,
they also have many different shapes.
Scale of the Universe
• http://htwins.net/scale2/
• Regardless of their size, shape or function,
cells have the same basic structure.
• Cells are highly organized and are very
complex. All cells have the following 3 main
parts:
• 1. The cell membrane.
• 2. The cytoplasm
• 3. The nucleus.
Cell Membrane
Nucleus
Cytoplasm
Cell membrane (plasma membrane)• surrounds cytoplasm of plant and animal cells.
Lies just inside the plant cell wall.
• Function – holds contents of the cell in place
•
- regulates the passage of materials into
and out of the cell, therefore is called
'selectively permeable’.
Cytoplasm
• everything inside the cell except the DNA
region (nucleus)
• Function - contains the cell structures (called
organelles - parts of a cell are often called
'organelles' which means 'little organs') that
are essential for the cell to function.
• - Cytoplasm is a jelly-like material, like
uncooked egg white, where many processes
are occurring at once, rather like a factory
Nucleus
• Function – holds the cell’s DNA and directs all
cell activities.
• “Control Centre” of the cell.
The nucleus is composed of :
• 1. Nuclear membrane (envelope) - a double
membrane (i.e. two membrane layers thick)
• Function - to separate the nuclear material (DNA)
from the rest of the cell
• Has very large nuclear pores to allow RNA to move
from the nucleus to the cytoplasm, but these pores
are too small to allow the chromosomes through.
The nucleus is composed of:
• 2. Chromatin or Chromosomes - Chromatin is called
chromosomes when it is coiled up into shorter
lengths. It contains complex molecules of DNA
(deoxyribonucleic acid) also known as genes.
• During regular cell activities, the chromatin is
uncoiled; it coils up into chromosomes prior to cell
division.
• Functions - 1. control all cell processes
2. carry the cell's heredity
The nucleus is composed of:
• 3. nucleolus - a dark region in the nucleus
• Function - believed to be the site of
synthesis of several kinds of RNA (ribonucleic
acid)
• Sometimes the DNA mutates that is, it
changes spontaneously and causes new
characteristics.
Mitochondria
• sausage shaped organelles which move
around with the cytoplasm.
• Function - sites of cell respiration (release of
energy from glucose and other foods for use
in the cell).
Ribosomes
• small oval structures composed of RNA and
protein
• Function - site of protein synthesis in cell
Endoplasmic Reticulum (ER)
• Canal-like arrangement of parallel membranes in
the cytoplasm but not in the nucleus.
• Rough Endoplasmic Reticulum has many
ribosomes attached to it.
– Function: 1. anchor ribosomes 2. carry proteins
through the cytoplasm
• Smooth Endoplasmic Reticulum - has no
ribosomes attached
– Function 1. anchor enzymes which synthesize fats or
lipids 2. transport fats and lipids through the
cytoplasm.
Golgi Apparatus (body, complex)
• formed of layers of membranes stacked on top
of each other, looks like a stack of pancakes.
• Functions 1. stores and secretes (ships out)
proteins and large molecules formed by the
cell 2. may be involved in forming the
endoplasmic reticulum
• Microfilaments – pipe-like structures made of
protein. Function – provide shape and
movement for the cell.
• Microtubules – thread-like protein. Function
– Transport internal structures through cells
(ie: chromosomes during cell division). Also
make up cilia and flagella.
Lysosomes
• Consist of a rounded membrane containing
enzymes which can digest the cell.
• Functions :
1. break down large molecules and cell parts within the
cytoplasm
2. digest food particles which can then be used by the
cell
3. destroy harmful substances which enter a cell
4. in white blood cells, destroy bacteria which have
entered your body
5. destroy worn out cells
Centrioles
• Tube-like structures found in animal cells, but
not plant cells.
• Function - appear to take part in cell division.
Vacuoles
• A fluid filled structure surrounded by a
membrane (called the vacuolar membrane) and
filled with different substances such as fat (in
animals) or water, salts and wastes.
• The vacuoles in animal cells are generally small,
but many plant cells have a large water-filled
central vacuole.
• Generally, vacuoles are not visible unless they
contain coloured molecules In plant cells, the
vacuole is often large and is found in the centre
of the cell; therefore it is called a central vacuole
Crash Course Eukaryotic Cells
• http://www.youtube.com/watch?v=cj8dDTHG
JBY
Structures and Organelles in
Plant Cells Only:
Plastids
• Plastids- Membrane sacs. Function: involved in
producing or storing food.
Types of plastids
• a) Chloroplasts – complex membrane structures
which contain chlorophyll. Function:Perform
photosynthesis (use Carbon Dioxide, water, and
sunlight to produce food and oxygen)
• b) Chromoplasts- contain pigments (color).
• c) Amyloplasts – colorless and store starch.
Cell Wall
• Non-living, made of cellulose molecules. Is
formed outside the plasma membrane Function:
surrounds, strengthens and protects the plant
cell.
•
Primary cell wall – thin, flexible, formed first.
Supports the plant
•
Secondary cell wall – is found around some
cells (i.e: wood), is thick and rigid, is
formed between the primary cell wall and the
plasma membrane. Supports the Plant.
?
• In plant cells, the vacuole is often large and is
found in the centre of the cell; therefore it is
called a central vacuole and contains water.
Crash Course Plant Cells
• http://www.youtube.com/watch?v=9UvlqAVC
oqY